The design of fatigue-prone structural elements such as wind turbine foundations requires adequate verification of the constituent materials to ascertain their resistance capacity under fatigue loading. Hence, the number of loading cycles that can be sustained in service using stress-life models, or the level of structural damage relative to a given limit, are required from the fatigue analysis of the structural components.

The presence of cracks in these structural components often renders them vulnerable to damage propagation because increased stresses in the steel reinforcing bars traversing cracked concrete planes may result in reinforcement crack initiation, and possibly propagation. As such, mediums involving the use of steel-fibre reinforced concrete have been adopted in designs to prevent or inhibit concrete crack evolution and reinforcement crack propagation under fatigue loading.

Investigations reported in the literature have shown that current fatigue resistance analysis approaches for concrete composites are insufficient, lack significant levels of reliance, and do not appropriately account for fatigue-governing mechanisms within a cracked concrete plane with intersecting reinforcement that exhibits progressive crack propagation. The effects of irreversible damage accumulation of concrete composites are often neglected, and damage models ignore important influencing factors;​ hence, they are limited to the analysis of structures with similar loading conditions as the test specimens used for developing such models.

An experimental campaign was conducted to develop robust damage models which account for relevant fatigue loading parameters. Various assumptions incorporated into fatigue analysis constitutive models were further verified to ascertain their conservative level and reliance. Based on the obtained results, a new analysis and design approach which accounts for irreversible damage accumulation of concrete composites (including steel fibres) is proposed. In addition, the complex behaviour at a concrete crack plane is considered by incorporating fracture mechanics and residual capacity models into the corresponding equilibrium equation, hence accounting for steel reinforcement crack propagation.

The proposed models were further incorporated into algorithms for strut and tie analysis and into the Disturbed Stress Field Model (finite element framework) for fatigue life and damage evolution predictions. Corroborated results of the experimental investigation conducted with the modified analysis approaches exhibited good correlation. From the verified improved analysis concepts and the unambiguity of the results interpretation, the proposed approach can be used for the fatigue resistance design and analysis of fatigue-prone structures in order to ascertain the required fatigue resistance capacity during service life.